Rear-Axle Spotter's Guide With Lug Patterns To Boot!

Not all of us are walking encyclopedias of automotive knowledge. We all know that one guy who can rattle off facts like how many '67 small-window C10s were made, but does that knowledge really matter? Well, it may not help build a truck, but it is cool to know. We wanted to give you some information that you might be able to use in the real world and hopefully help you build a better truck. With the assistance of some of our four-wheel-drive buddies, we compiled a guide to help you determine what rearend is under the truck and what lug pattern it has. This will just cover truck stuff, but that doesn't mean a car rearend can't be stuffed under your S-10. But that's a story for another day. We hope you find this guide useful, and until next month: Keep your eyes on the rearend.

TECH TIPAxle TerminologyTo prevent you from looking like a total newbie, here's some techno-jargon terms you should know when talking to the guy behind the parts counter:

Semifloating: The weight of the vehicle rides on the axleshaft, which also spins the wheel.

Full-floating: The weight of the vehicle rides on the axlehousing, and a ring of bolts in the center holds the axleshaft in place.

Integral: The ring gear and pinion gear are set up inside the differential housing.

Dropout: The carrier, or differential, can be removed as a single unit. It is also called the centersection.

Ford 9-InchAppearing in almost every light truck with Ford written on the tailgate, the Ford 9-inch is one of the strongest light-axle designs around. Though production ceased several years ago, these units are still plentiful in wrecking yards, not to mention from custom-axle builders. The 9-inch is easily spotted because it uses a third member, or dropout, to house the ring-and-pinion, making it accessible from the front rather than the rear of the axle. This means there is no bolt pattern to look for, only a round hump.Applications: '66-'88 Bronco, '57-'87 F-100/F-150/F-250Ring-gear diameter: 9 inPinion-gear diameter/splines: 1.313 in/28 and 31 splinesAvailable gearsets: 2.80, 2.86, 2.94, 3.00, 3.10, 3.15, 3.25, 3.40, 3.50, 3.55, 3.60, 3.64, 3.70, 3.75, 3.80, 3.82, 3.89, 3.91, 4.00, 4.11, 4.22, 4.30, 4.33, 4.40, 4.50, 4.56, 4.57, 4.63, 4.71, 4.78, 4.86, 5.00, 5.14, 5.22, 5.29, 5.43, 5.50, 5.57, 5.67, 5.83, 6.00, 6.14, 6.20, 6.33, and 6.50

GM 9-1/2-INCH & 10-1/2-INCH 14-BOLT GM produced two 14-bolt axles through the years: the 9-1/2-inch and the 10-1/2-inch (shown). The 10-1/2-inch is the stronger of the two. Both use 14-bolt covers, but the 9-1/2 is more egg-shaped (like a larger GM 7-1/2), while the 10-1/2 has straight sides and sharper corners. The 9-1/2 is an integral pinion design where the pinion is removed through the rear cover plate. The 10-1/2 is a removable pinion design, which allows the pinion to be removed from the front of the housing without pulling the rear cover. Other distinguishing features of the 10-1/2 are the 6-bolt removable pinion support and full-floating axles.Applications: '88-'96 C10/C15/C20 (9-1/2-inch), '88-'96 K10/K15, '81-'96 K20, '73-'92 K2500/K3500 (10-1/2-inch)Ring-gear diameter: 9-1/2 in, 10-1/2 inPinion-gear diameter/splines: 1.876 in/30 splines (9-1/2), 1.750 in/30 splines (10-1/2)Available gearsets:3.42, 3.73, 4.10, 4.56, 4.88, 5.13 (10-1/2 only)

GM 12-Bolt Two versions of the GM 12-bolt exist but have nothing more than the bolt count in common. One is a car version with a grooved cover plate, while the truck-version cover plate is raised. The 12-bolt is integral and semifloating, but isn't a big step up from the 8-1/2-inch 10-bolt because the axleshafts and housings are very similar. A drawback to both the 10- and 12-bolt axles is that the axleshafts are retained by C-clips, which, if broken, can be a serious hazard.Applications: '64-'82 K10/K20 and BlazerRing-gear diameter: 8.875 inPinion-gear diameter/splines: 1.438/30 splinesAvailable gearsets: 3.07, 3.42, 3.73, 4.10, 4.56, 4.88, 5.13, and 5.38

Toyota 8-InchAlso referred to as a 7.8-inch (Americans rounded up the figure), two versions of the 8-inch appeared in Toyotas over the years: one for four-cylinder applications and another for the turbo four-cylinder and V-6 models. The only difference between the two is that the four-cylinder model uses shorter pinion gears. Both units are dropouts and are recognizable by the nonremovable, humped rear cover and breather tube on the top of the housing. Applications: '79-'85 Toyota (four-cylinder model), '86-'96 Toyota, '86-'96 Toyota (turbo/V-6 model)Ring-gear diameter: 7.8 inPinion-gear diameter/splines: 1.378 in/27 splinesAvailable gearsets: 3.70, 3.90, 4.11, 4.37, 4.56, 4.88, 5.29, and 5.71

Dana 44 The Dana 44 went into production in the late '40s and has since appeared in virtually every make of production four-wheel-drive vehicle. On the street side, the 44 found its way into some Chevys and Fords. It has a 10-bolt cover design and was produced with 30-spline axleshafts.Applications: '60-'70 C10/15, '67-'78 F-100/F-150 4x4Ring-gear diameter: 8.5 inPinion-gear diameter/splines: 1.376/30 splinesAvailable gearsets: 2.72, 2.87, 3.07, 3.23, 3.31, 3.54, 3.73, 3.92, 4.09, 4.27, 4.56, 4.89, 5.38, and 5.89

Dana 60 (also 50) Looking like a larger version of the Dana 44, the Dana 60 can be identified by its 12-bolt pattern. The housing is made from nodular iron, which provides excellent rigidity and strength over other housings. Still in production today, the Dana 60 is offered in both semi- and full-floating configurations and is touted as one of the strongest and most reliable units available.Applications: '67-'85 F-100, '67-'85 F-150, '67-'92 F-250, '78-'92 F-350, numerous Chevrolet, Dodge 3/4- and 1-tonRing-gear diameter: 9.75 inPinion-gear diameter/splines: 1.626 in/30 and 35 splinesAvailable gearsets: 3.33, 3.54, 3.73, 4.10, 4.56, 4.88, 5.13, 5.38, 5.57, 5.86, 6.17, and 7.17

The Final Word Armed with this info, you should be able to know your rearends and what they fit and what gears you can get. The lug pattern sidebar should help you determine if you can stuff those sweet Escalade wheels your buddy has on your Nissan pickup.